The present invention relates to an expansion bolt, particularly for use in engaging drilled holes. The application incorporates by reference herein in its entirety the inventors"" U.S. Pat. No. 6,109,578, wherein a description of the related art as it concerns rock climbing is provided. The borehole-engaging apparatus of the ""578 patent provides a number of advantages over the prior art, such as simple construction, reliable operation, greater standardization, which reduces the cost per unit and the amount of gear that a climber must purchase and carry, and robustness or insensitivity to rotational orientation about the apparatus"" longitudinal axis. For many purposes, including rock climbing, it is particularly important that the expansion bolt be easily removable. The lack of this feature is exemplified by an embodiment of an anchoring device shown in FIG. 3 of Dohmieier, U.S. Pat. No. 3,478,641, which biases hole gripping dogs outwardly with a brindle which is not accessible for removing the device.
The novel expansion bolt of the present invention provides advantages similar to those of the ""578 patent, as well as outstanding ease of insertion and removal, and hole-engaging or holding strength.
In addition to the problems associated with anchoring to rocks for rock climbing, the construction industry and providers of emergency services such as fire, police and rescue service often have the need for anchoring structures or devices for temporary use. For example, temporary shelter may be needed, and tents may need to be erected quickly in urban environments, i.e., on concrete or asphalt surfaces. To anchor the tent, weights such as sand bags or drums of water are typically employed. However, the use of weights poses a difficulty in obtaining and moving the material for the weights, or in obtaining and moving the weights themselves. These aspects of the use of weights as anchors as well as other aspects of the weights, such as the ready availability of sand or dirt in the urban environment, make it more difficult to move and erect the tent quickly.
In the construction industry, it is often imperative to provide fall protection for the workers. Typically, contractors build-in specialized harnessing hardware at predetermined locations on or in the structures as they are built. The harnessing hardware is specially adapted to accept inserts that are difficult to use because they tend to fill up with concrete. As the locations for the built-in hardware are predetermined, it may be determined later that they have not been placed precisely where they are needed, yet they will often be used anyway, posing risk of extreme injury or death. Moreover, as permanent or semi-permanent installations, they may be used by subcontractors or others when this is not anticipated or desired, so that the contractor assumes a risk of liability for injuries or deaths that result from the imprudent use of the harnessing hardware by others.
Also in the construction industry, there is often a need to move large objects or materials, such as boulders. Irregularly shaped objects such as boulders present particular difficulties in grasping; often chains must be wrapped around a boulder or other irregularly shaped object to secure it. Prefabricated structural materials, such as concrete facades, are typically provided with hardware for attaching chains or cables; however, these also may be found insufficient during actual construction.
There is also a need for retrofitting bridges and other structures with tying cables to increase earthquake resistance, and tying one or more large objects together. Presently, the cables are secured to hardware which is bolted to the structure with a number of bolts, requiring that a number of corresponding holes be drilled in the structure.
Emergency workers must sometimes assemble structures used for maneuvering in urban environments quickly, to respond to man-made and natural disasters. For example, emergency workers may need to climb the face of buildings, or provide hoists for elevating people and equipment, or anchor ladders to man-made structures such as brick or concrete-faced buildings as well as natural features such as rocks.
Accordingly, there is a need for an expansion bolt that provides a simple, reliable and relatively inexpensive means for connecting a cable, rope or wire to a drilled hole in a hard material, that is easy to install in and remove from the hole, and that effectively anchors to the hole while applying a minimum stress to the hole, while providing a minimum sensitivity to the angular orientation of the expansion bolt in the hole. There is more particularly a need to provide all of these features for use in a hole drilled in concrete or another hard but relatively brittle or weak material.
The expansion bolt of the present invention solves the aforementioned problems and meets the aforementioned needs by providing a first chock having first and second outer ramping surfaces, a second chock having an inner ramping surface complementarily corresponding to the first outer ramping surface and a first spring member for biasing the second chock radially inwardly toward the axis against the first outer ramping surface of the first chock.
Preferably, a third chock is provided having an inner ramping surface complementarily corresponding to the second outer ramping surface, along with a second spring member for biasing the third chock radially inwardly toward the axis against the second outer ramping surface of the first chock.
Preferably, the center chock is frustoconical and the ramping surface thereof is convex, and the outer chock has a complementary frustoconical ramping surface that is concave. Preferably, at least two outer chocks are azimuthally symmetrically disposed about the longitudinal axis.
Therefore, it is a principal object of the present invention to provide a novel and improved expansion bolt.
It is a further object of the present invention to provide an expansion bolt that provides a simple, reliable and relatively inexpensive means for connecting a cable, rope or wire to a hole drilled in a hard material.
It is still a further object of the present invention to provide an expansion bolt that facilitates insertion into the hole and removal from the hole.
It is yet a further object of the present invention to provide an expansion bolt that provides for effectively anchoring to the hole while applying a minimum stress to the hole.
It is another object of the present invention to provide an expansion bolt that provides minimum sensitivity to the angular orientation of the expansion bolt in the hole.
It is still another object of the present invention to provide an expansion bolt that provides for increased holding strength in holes drilled in relatively brittle or weak materials such as concrete and asphalt.
It is yet another object of the present invention to provide an expansion bolt for use in such materials that minimizes the stress placed on the material.
It is still a further object of the present invention to provide an expansion bolt for use in such materials that more uniformly distributes the stress placed on the material.
The foregoing and other objects, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the following drawings.